Role In Skeletal Muscle Development Research Articles

Identification of relevant differential genes to the divergent devel-opment of pectoral muscle in ducks by transcriptomic analysis.

The objective of this study was to identify candidate genes that play im-portant roles in skeletal muscle development in ducks. In this study, we investigated the transcriptional sequencing of embryonic pectoral muscles from two specialized line LCA and LCC ducks which were devel-oped from Liancheng White ducks (female) and Cherry Valley ducks (male) F6 hybrid population. In addition, prediction of target genes for the differentially expressed mRNAs was conducted and the enriched gene ontology (GO) terms and Kyoto En-cyclopedia of Genes and Genomes (KEGG) signaling pathways were further analyzed. Finally, a protein-to-protein interaction (PPI) network was analyzed by using the tar-get genes to gain insights into their potential functional association. A total of 1428 differentially expressed genes (DEGs) with 762 being up-regulated genes and 666 being down-regulated genes in pectoral muscle of LCA and LCC ducks identified by RNA-seq (p < 0.05). Meanwhile, 23 GO terms in the down-regulated genes and 75 GO terms in up-regulated genes were significantly en-riched (p < 0.05). Furthermore, the top 5 most enriched pathways were ECM-receptor interaction, fatty acid degradation, pyruvate degradation, PPAR signaling pathway, and glycolysis/gluconeogenesis. Finally, the candidate genes including Integrin b3 (Itgb3), Pyruvate kinase M1/2 (Pkm), Insulin-like growth factor 1 (Igf1), glu-cose-6-phosphate isomerase（Gpi）, GABA type A receptor-associated protein-like 1(Gabarapl1), and Thyroid hormone receptor beta (Thrb) showed the most expression difference, and then were selected to verification by qRT-PCR. The result of qRT-PCR was consistent with that of transcriptome sequencing. This study provided information of molecular mechanisms underlying the developmental differences in skeletal muscles between specialized duck lines.

Identification of circRNA-associated ceRNA networks in the longissimus dorsi of yak under different feeding systems

BackgroundYaks (Bos grunniens), prized for their ability to thrive in high-altitude environments, are indispensable livestock in the plateau region. Modifying their feeding systems holds significant promise for improving their growth and meat quality. Tenderness, a key determinant of yak meat quality and consumer appeal, is demonstrably influenced by dietary regimen. Indoor feeding regimes have been shown to enhance tenderness by lowering shear stress and optimizing pH values. CircRNAs, well-known modulators of circulatory function, also play a crucial role in skeletal muscle development across various animal species. However, their functional significance in yak skeletal muscle remains largely unexplored.ResultsIn this study, we identified a total of 5,534 circRNAs within the longissimus dorsi muscle, and we found 51 differentially expressed circRNAs (20 up-regulated and 31 down-regulated) between the two feeding groups. Constructing a comprehensive ceRNA network illuminated intricate regulatory mechanisms, with PGP and circRNA_0617 converging on bta-miR-2285q, mirrored by KLF15/circRNA_0345/bta-miR-20b and CTSF/circRNA_0348/bta-miR-146a. These findings shed light on the potential of circRNAs to influence yak muscle development and meat quality, offering valuable insights for future research.ConclusionsThis investigation unraveled a complex interaction network between circRNAs、mRNAs and miRNAs in yak skeletal muscle. We further elucidated the target genes regulated by these target genes within the network, offering valuable insights into the potential regulatory mechanisms governing muscle development and meat quality-related traits in yaks.

Loss of lysosomal acid lipase results in mitochondrial dysfunction and fiber switch in skeletal muscles of mice

ObjectiveLysosomal acid lipase (LAL) is the only enzyme known to hydrolyze cholesteryl esters (CE) and triacylglycerols in lysosomes at an acidic pH. Despite the importance of lysosomal hydrolysis in skeletal muscle (SM), research in this area is limited. We hypothesized that LAL may play an important role in SM development, function, and metabolism as a result of lipid and/or carbohydrate metabolism disruptions. ResultsMice with systemic LAL deficiency (Lal−/−) had markedly lower SM mass, cross-sectional area, and Feret diameter despite unchanged proteolysis or protein synthesis markers in all SM examined. In addition, Lal−/− SM showed increased total cholesterol and CE concentrations, especially during fasting and maturation. Regardless of increased glucose uptake, expression of the slow oxidative fiber marker MYH7 was markedly increased in Lal−/−SM, indicating a fiber switch from glycolytic, fast-twitch fibers to oxidative, slow-twitch fibers. Proteomic analysis of the oxidative and glycolytic parts of the SM confirmed the transition between fast- and slow-twitch fibers, consistent with the decreased Lal−/− muscle size due to the “fiber paradox”. Decreased oxidative capacity and ATP concentration were associated with reduced mitochondrial function of Lal−/− SM, particularly affecting oxidative phosphorylation, despite unchanged structure and number of mitochondria. Impairment in muscle function was reflected by increased exhaustion in the treadmill peak effort test in vivo. ConclusionWe conclude that whole-body loss of LAL is associated with a profound remodeling of the muscular phenotype, manifested by fiber type switch and a decline in muscle mass, most likely due to dysfunctional mitochondria and impaired energy metabolism, at least in mice.

LncRNA GPRC5D-AS1 as a ceRNA inhibits skeletal muscle aging by regulating miR-520d-5p.

Sarcopenia induced by muscle aging is associated with negative outcomes in a variety of diseases. Long non-coding RNAs are a class of RNAs longer than 200 nucleotides with lower protein coding potential. An increasing number of studies have shown that lncRNAs play a vital role in skeletal muscle development. According to our previous research, lncRNA GPRC5D-AS1 is selected in the present study as the target gene to further study its effect on skeletal muscle aging in a dexamethasone-induced human muscle atrophy cell model. As a result, GPRC5D-AS1 functions as a ceRNA of miR-520d-5p to repress cell apoptosis and regulate the expression of muscle regulatory factors, including MyoD, MyoG, Mef2c and Myf5, thus accelerating myoblast proliferation and differentiation, facilitating development of skeletal muscle. In conclusion, lncRNA GPRC5D-AS1 could be a novel therapeutic target for treating sarcopenia.

Candidate circRNAs related to skeletal muscle development in Dazu black goats

Circular RNA (CircRNA), as a classical noncoding RNA, has been proven to regulate skeletal muscle development (SMD). However, the molecular genetic basis of circRNA regulation in muscle cells remains unclear. In this study, the expression patterns of circRNAs in the longissimus dorsi muscle at embryonic day 75 and postnatal day 1 in DBGs were investigated to identify the key circRNAs that play an important role in SMD in goats. A total of 140 significantly and differentially expressed circRNAs (DEcircRNAs) were identified among the groups at different developmental stages. Among the 116 host genes (HGs) of DEcircRNAs, 76 were significantly and differentially expressed, which was confirmed by previous RNA_seq data. Furthermore, the expression pattern of 10 DEcircRNAs with RT-qPCR was verified, which showed 80% concordance rate with that of RNA_seq datasets. Moreover, the authenticity of seven randomly selected DEcircRNAs was verified by PCR Sanger sequencing. Based on the functional annotation results, among the 76 significantly and differentially expressed HGs, 74 were enriched in 845 GO terms, whereas 35 were annotated to 85 KEGG pathways. The results of this study could provide a comprehensive understanding of the genetic basis of circRNAs involved in SMD and muscle growth.

Ythdf2-mediated STK11 mRNA decay supports myogenesis by inhibiting the AMPK/mTOR pathway

An emerging research focus is the role of m6A modifications in mediating the post-transcriptional regulation of mRNA during mammalian development. Recent evidence suggests that m6A methyltransferases and demethylases play critical roles in skeletal muscle development. Ythdf2 is a m6A “reader” protein that mediates mRNA degradation in an m6A-dependent manner. However, the specific function of Ythdf2 in skeletal muscle development and the underlying mechanisms remain unclear. Here, we observed that Ythdf2 expression was significantly upregulated during myogenic differentiation, whereas Ythdf2 knockdown markedly inhibited myoblast proliferation and differentiation. Combined analysis of high-throughput sequencing, Co-IP, and RIP assay revealed that Ythdf2 could bind to m6A sites in STK11 mRNA and form an Ago2 silencing complex to promote its degradation, thereby regulating its expression and consequently, the AMPK/mTOR pathway. Furthermore, STK11 downregulation partially rescued Ythdf2 knockdown-induced impairment of proliferation and myogenic differentiation by inhibiting the AMPK/mTOR pathway. Collectively, our results indicate that Ythdf2 mediates the decay of STK11 mRNA, an AMPK activator, in an Ago2 system-dependent manner, thereby driving skeletal myogenesis by suppressing the AMPK/mTOR pathway. These findings further enhance our understanding of the molecular mechanisms underlying RNA methylation in the regulation of myogenesis and provide valuable insights for conducting in-depth studies on myogenesis.

CircGUCY2C regulates cofilin1 by sponging miR-425-3p to promote the proliferation of porcine skeletal muscle satellite cells.

Circular ribonucleic acids (or circRNAs) are an emerging class of endogenous noncoding RNAs that are involved in physiological and pathological processes. Increasing evidence suggests that circRNAs play an important regulatory role in skeletal muscle development and meat quality regulation. In this study, it was found that circGUCY2C exhibits a high expression level in the longissimus dorsi muscle. It shows resistance to RNase R and additionally promotes the mRNA expression of cyclin-dependent kinase 2 (CDK2) and proliferating cell nuclear antigen (PCNA). Specifically, it was observed that the overexpression of circGUCY2C could promote the transition of porcine skeletal muscle satellite cells into the S and G2 phases of the cell cycle and that it regulates the proliferation of porcine skeletal muscle satellite cells. In contrast, miR-425-3p plays the opposite role and has an inhibitory effect on the proliferation of porcine skeletal muscle satellite cells. MiR-425-3p has been described as a target of circGUCY2C; consequently, the depletion of miR-425-3p promoted the proliferation of porcine skeletal muscle satellite cells. CFL1 (cofilin 1) is a target of miR-425-3p, and circGUCY2C upregulated CFL1 expression by inhibiting miR-425-3p. Collectively, our research outcomes demonstrate that circGUCY2C significantly influences the proliferation of porcine skeletal muscle satellite cells by selectively targeting the miR-425-3p-CFL1 axis, and our work partially clarified the role of circGUCY2C in porcine skeletal muscle satellite cells. Thus, the study provides new insight into the function of circGUCY2C and adds to the knowledge of the post-transcriptional regulation of pork quality.

KLF4 regulates skeletal muscle development and regeneration by directly targeting P57 and Myomixer

Krüppel-like factor 4 (KLF4) is an evolutionarily conserved zinc finger-containing transcription factor that regulates diverse cellular processes such as cell proliferation, apoptosis, and differentiation. Our previous study showed that KLF4 expression is upregulated in skeletal muscle ontogeny during embryonic development in pigs, suggesting its importance for skeletal muscle development and muscle function. We revealed here that KLF4 plays a critical role in skeletal muscle development and regeneration. Specific knockout of KLF4 in skeletal muscle impaired muscle formation further affecting physical activity and also defected skeletal muscle regeneration. In vitro, KLF4 was highly expressed in proliferating myoblasts and early differentiated cells. KLF4 knockdown promoted myoblast proliferation and inhibited myoblast fusion, while its overexpression showed opposite results. Mechanically, in proliferating myoblasts, KLF4 inhibits myoblast proliferation through regulating cell cycle arrest protein P57 by directly targeting its promoter; while in differentiated myoblasts, KLF4 promotes myoblast fusion by transcriptionally activating Myomixer. Our study provides mechanistic information for skeletal muscle development, reduced muscle strength and impaired regeneration after injury and unveiling the mechanism of KLF4 in myogenic regulation.

Feet and legs malformation in Nellore cattle: genetic analysis and prioritization of GWAS results.

Beef cattle affected by feet and legs malformations (FLM) cannot perform their productive and reproductive functions satisfactorily, resulting in significant economic losses. Accelerated weight gain in young animals due to increased fat deposition can lead to ligaments, tendon and joint strain and promote gene expression patterns that lead to changes in the normal architecture of the feet and legs. The possible correlated response in the FLM due to yearling weight (YW) selection suggest that this second trait could be used as an indirect selection criterion. Therefore, FLM breeding values and the genetic correlation between FLM and yearling weight (YW) were estimated for 295,031 Nellore animals by fitting a linear-threshold model in a Bayesian approach. A genome-wide association study was performed to identify genomic windows and positional candidate genes associated with FLM. The effects of single nucleotide polymorphisms (SNPs) on FLM phenotypes (affected or unaffected) were estimated using the weighted single-step genomic BLUP method, based on genotypes of 12,537 animals for 461,057 SNPs. Twelve non-overlapping windows of 20 adjacent SNPs explaining more than 1% of the additive genetic variance were selected for candidate gene annotation. Functional and gene prioritization analysis of candidate genes identified six genes (ATG7, EXT1, ITGA1, PPARD, SCUBE3, and SHOX) that may play a role in FLM expression due to their known role in skeletal muscle development, aberrant bone growth, lipid metabolism, intramuscular fat deposition and skeletogenesis. Identifying genes linked to foot and leg malformations enables selective breeding for healthier herds by reducing the occurrence of these conditions. Genetic markers can be used to develop tests that identify carriers of these mutations, assisting breeders in making informed breeding decisions to minimize the incidence of malformations in future generations, resulting in greater productivity and animal welfare.

Different levels of autophagy induced by transient serum starvation regulate metabolism and differentiation of porcine skeletal muscle satellite cells

This study aimed to investigate the effects of different levels of autophagy induced by transient serum starvation on the metabolism, lipid metabolism, and differentiation of porcine skeletal muscle satellite cells (SMSCs) to preliminary elucidate the role and function of autophagy in the regulatory network of skeletal muscle development. Different levels of autophagy were induced by controlling the serum concentration in the culture system for 24 h. Apoptosis, membrane potential, reactive oxygen species (ROS), ATP, and myogenic and lipogenic differentiation markers were monitored to determine if autophagy affected the metabolism and differentiation of SMSCs. Autophagy was induced in SMSCs via serum starvation (5%, 15%), as evidenced by decreased p62 and mTOR phosphorylation levels and increased LC3B lipidation and AMPK phosphorylation levels. Transmission electron microscopy revealed the presence of autophagosomes, and the rates of morphologically abnormal nuclei and mitochondria gradually increased with the decrease in serum concentration, the number of autophagic lysosomes also increased, indicating that 5% serum starvation induced severe autophagy, while 15% serum starvation induced mild autophagy. Compared with the control group and 15% serum-starved SMSCs, SMSCs undergoing 5% serum starvation had the highest intracellular ATP and ROS levels, the highest percentage of apoptotic cells, and the lowest membrane potential. The 15% serum-starved SMSCs had the highest membrane potential, but the percentage of apoptotic cells did not change significantly compared with the control group. The levels of the myogenic markers MyoD1 and MHC were significantly higher in 15% serum-starved SMSCs than in serum-sufficient SMSCs and the lowest in the 5% serum-starved SMSCs. The lipid contents (measured by Oil Red O staining and quantification of triglycerides) and lipogenic markers Peroxisome Proliferators-activated Receptors γ and Lipoprotein Lipase were also significantly higher in SMSCs undergoing 15% serum starvation than in the control group, and the lowest in the 5% serum-starved SMSCs. Different levels of starvation stress induce different levels of autophagy. Mild autophagy induced by moderate serum starvation promotes the metabolism and differentiation of SMSCs, while severe autophagy renders SMSCs more apoptotic, abnormal metabolism and suppresses SMSC differentiation into adipocytes or myocytes, and reduces lipid metabolisms. Our study suggests that autophagy plays a role in skeletal muscle development and may help design strategies for improving meat production traits in domestic pigs.

Transcriptome-Based Identification of the Muscle Tissue-Specific Expression Gene CKM and Its Regulation of Proliferation, Apoptosis and Differentiation in Chicken Primary Myoblasts.

Skeletal muscle is an essential tissue in meat-producing animals, and meat-producing traits have been a hot topic in chicken genetic breeding research. Current research shows that creatine kinase M-type-like (CKM) is one of the most abundant proteins in skeletal muscle and plays an important role in the growth and development of skeletal muscle, but its role in the development of chicken skeletal muscle is still unclear. Via RNA sequencing (RNA-seq), we found that CKM was highly expressed in chicken breast muscle tissue. In this study, the expression profile of CKM was examined by quantitative real-time PCR (qPCR), and overexpression and RNA interference techniques were used to explore the functions of CKM in the proliferation, apoptosis and differentiation of chicken primary myoblasts (CPMs). It was shown that CKM was specifically highly expressed in breast muscle and leg muscle and was highly expressed in stage 16 embryonic muscle, while CKM inhibited proliferation, promoted the apoptosis and differentiation of CPMs and was involved in regulating chicken myogenesis. Transcriptome sequencing was used to identify genes that were differentially expressed in CPMs after CKM disruption, and bioinformatics analysis showed that CKM was involved in regulating chicken myogenesis. In summary, CKM plays an important role in skeletal muscle development during chicken growth and development.

Circular Intronic RNA circTTN Inhibits Host Gene Transcription and Myogenesis by Recruiting PURB Proteins to form Heterotypic Complexes.

Muscle cell growth plays an important role in skeletal muscle development. Circular RNAs (circRNAs) have been proven to be involved in the regulation of skeletal muscle growth and development. In this study, we explored the effect of circTTN on myoblast growth and its possible molecular mechanism. Using C2C12 cells as a functional model, the authenticity of circTTN was confirmed by RNase R digestion and Sanger sequencing. Previous functional studies have showed that the overexpression of circTTN inhibits myoblast proliferation and differentiation. Mechanistically, circTTN recruits the PURB protein on the Titin (TTN) promoter to inhibit the expression of the TTN gene. Moreover, PURB inhibits myoblast proliferation and differentiation, which is consistent with circTTN function. In summary, our results indicate that circTTN inhibits the transcription and myogenesis of the host gene TTN by recruiting PURB proteins to form heterotypic complexes. This work may act as a reference for further research on the role of circRNA in skeletal muscle growth and development.

Natural antisense transcript of MYOG regulates development and regeneration in skeletal muscle by shielding the binding sites of MicroRNAs of MYOG mRNA 3′UTR

Natural antisense transcripts (NATs) are endogenous RNAs opposite to sense transcripts, and they can significantly contribute to regulating various biological processes through multiple epigenetic mechanisms. NATs can affect their sense transcripts to regulate the growth and development of skeletal muscle. Our analysis of third-generation full-length transcriptome sequencing data revealed that NATs represented a significant portion of the lncRNA, accounting for up to 30.19%–33.35%. The expression of NATs correlated with myoblast differentiation, and genes expressing NATs were mainly involved in RNA synthesis, protein transport, and cell cycle. We found a NAT of MYOG (MYOG-NAT) in the data. We found that the MYOG-NAT could promote the differentiation of myoblasts in vitro. Additionally, knockdown of MYOG-NAT in vivo led to muscle fiber atrophy and muscle regeneration retardation. Molecular biology experiments demonstrated that MYOG-NAT enhances the stability of MYOG mRNA by competing with miR-128-2-5p, miR-19a-5p, and miR-19b-5p for binding to MYOG mRNA 3′UTR. These findings suggest that MYOG-NAT plays a critical role in skeletal muscle development and provides insights into the post-transcriptional regulation of NATs.

Unravelling the Effects of Syndecan-4 Knockdown on Skeletal Muscle Functions.

The remodelling of the extracellular matrix plays an important role in skeletal muscle development and regeneration. Syndecan-4 is a cell surface proteoglycan crucial for muscle differentiation. Syndecan-4-/- mice have been reported to be unable to regenerate following muscle damage. To investigate the consequences of the decreased expression of Syndecan-4, we have studied the in vivo and in vitro muscle performance and the excitation-contraction coupling machinery in young and aged Syndecan-4+/- (SDC4) mice. In vivo grip force was decreased significantly as well as the average and maximal speed of voluntary running in SDC4 mice, regardless of their age. The maximal in vitro twitch force was reduced in both EDL and soleus muscles from young and aged SDC4 mice. Ca2+ release from the sarcoplasmic reticulum decreased significantly in the FDB fibres of young SDC4 mice, while its voltage dependence was unchanged regardless of age. These findings were present in muscles from young and aged mice as well. On C2C12 murine skeletal muscle cells, we have also found altered calcium homeostasis upon Syndecan-4 silencing. The decreased expression of Syndecan-4 leads to reduced skeletal muscle performance in mice and altered motility in C2C12 myoblasts via altered calcium homeostasis. The altered muscle force performance develops at an early age and is maintained throughout the life course of the animal until old age.

Targeted Demethylation of the TGFβ1 mRNA Promotes Myoblast Proliferation via Activating the SMAD2 Signaling Pathway.

Recent evidence suggested that N6-methyladenosine (m6A) methylation can determine m6A-modified mRNA fate and play an important role in skeletal muscle development. It was well known that transforming growth factor beta 1 (TGFβ1) is involved in a variety of cellular processes, such as proliferation, differentiation, and apoptosis. However, little is known about the m6A-mediated TGFβ1 regulation in myogenesis. Here, we observed an increase in endogenous TGFβ1 expression and activity during myotube differentiation. However, the knockdown of TGFβ1 inhibits the proliferation and induces cell apoptosis of myoblast. Moreover, we found that m6A in 5'-untranslated regions (5'UTR) of TGFβ1 promote its decay and inhibit its expression, leading to the blockage of the TGFβ1/SMAD2 signaling pathway. Furthermore, the targeted specific demethylation of TGFβ1 m6A using dCas13b-FTO significantly increased the TGFβ1-mediated activity of the SMAD2 signaling pathway, promoting myoblast proliferation. These findings suggest that TGFβ1 is an essential regulator of myoblast growth that is negatively regulated by m6A. Overall, these results highlight the critical role of m6A-mediated post-transcriptional regulation in myogenesis.

Transcription factor ZBTB42 is a novel prognostic factor associated with immune cell infiltration in glioma.

Background: ZBTB42 is a transcription factor that belongs to the ZBTB transcript factor family and plays an important role in skeletal muscle development. Dysregulation of ZBTB42 expression can lead to a variety of diseases. However, the function of ZBTB42 in glioma development has not been studied by now. Methods: We analyzed the expression of ZBTB42 in LGG and GBM via the The Cancer Genome Atlas CGA and Chinese Glioma Genome Atlas database. Gene Ontology, KEGG, and GSVA analyses were performed to illustrate ZBTB42-related pathways. ESTIMATE and CIBERSORT were applied to calculate the immune score and immune cell proportion in glioma. One-class logistic regression OCLR algorithm was used to study the stemness of glioma. Multivariate Cox analysis was employed to detect the prognostic value of five ZBTB42-related genes. Results: Our results show that ZBTB42 is highly expressed in glioma and may be a promising prognostic factor for Low Grade Glioma and GBM. In addition, ZBTB42 is related to immune cell infiltration and may play a role in the immune suppression microenvironment. What's more, ZBTB42 is correlated with stem cell markers and positively associated with glioma stemness. Finally, a five genes nomogram based on ZBTB42 was constructed and has an effective prognosis prediction ability. Conclusion: We identify that ZBTB42 is a prognostic biomarker for Low Grade Glioma and GBM and its function is related to the suppressive tumor microenvironment and stemness of glioma.

Molecular characterization, expression pattern and genetic variant of insulin-like growth factor 2 mRNA-binding protein 3 gene in goose (Anser cygnoides)

ABSTRACT As a member of the insulin-like growth factor mRNA binding proteins (IGFBPs) family, IGF2BP3 plays important role in skeletal muscle development by regulating IGF2, which has been considered a key gene related to growth and reproductive traits in many agricultural animal species. However, study on the goose IGF2BP3 gene is still scarce. In this study, the full-length cDNA sequence of goose IGF2BP3 gene was cloned and characterized. The goose IGF2BP3 cDNA is 1825 bp in length, containing an open reading frame (ORF) of 1755 bp that encodes a protein of 584 amino acids, which consists of two RNA-recognition motifs (RRMs) and four K-homologous (KH) domains. RT-qPCR analysis indicates that the IGF2BP3 mRNA expression level is the highest in ovary tissue, followed in hypothalamus, spleen, leg muscle and liver, and low level in breast muscle and muscular stomach of the adult Zhedong White goose. Meanwhile, 25 single nucleotide polymorphisms (SNPs) and 5 insertions/deletions (InDels) variants were identified in about 10,764 bp of goose IGF2BP3 genomic DNA sequence. These results serve as a foundation for further investigations of the function of IGF2BP3 gene in geese.

MiR-495-3p regulates myoblasts proliferation and differentiation through targeting cadherin 2

MircoRNAs (miRNAs) play an important role in skeletal muscle development. Previous study had found that miR-495-3p was differentially expressed in fetal and adult goat skeletal muscle, but its function in myogenic proliferation and differentiation are unclear. Herein, we found the expression of miR-495-3p in C2C12 was downregulated during proliferation stage and upregulated during differentiation stage. Functionally, overexpression of miR-495-3p in C2C12 inhibited proliferation, and promoted myogenic differentiation. Mechanistically, the luciferase reporter assay demonstrated that cadherin 2 (CDH2) was a potential target gene of miR-495-3p. Importantly, overexpression of miR-495-3p inhibited CDH2 expression. Furthermore, knockdown of CDH2 in C2C12 inhibited proliferation and promoted myogenic differentiation. Together, the results showed that miR-495-3p inhibits C2C12 proliferation and promotes myogenic differentiation through targeting CDH2.

CircRNA: Its biogenesis and role in skeletal muscle development

Previously, circRNAs considered splicing errors during transcription, but recent studies uncovered that circRNA is a new group of noncoding RNAs. CircRNAs are produced through back splicing of pre mRNA and have more stability than linear RNA due to its closed loop structure. Numerous studies have unveiled the regulatory functions of circRNA in various biological mechanisms. Current literature has observed that circRNAs regulate the myogenesis of skeletal muscles through sponging miRNAs or acting as competitive endogenous RNA (CeRNA). Apart from myogenesis, it also regulates the functioning of different proteins at the molecular level and plays a key role during translation or protein encoding. All these facts have opened a new arena of research regarding the regulation of gene expression. This study aims to discuss the research advancements and new developments in the regulatory functions of circRNAs, including the development of skeletal muscle. This study also intends to discuss some newly discovered circRNAs involved in skeletal muscle development, especially in chicken and cattle.

Transcriptome-wide study revealed m6A and miRNA regulation of embryonic breast muscle development in Wenchang chickens.

N6-Methyladenosine (m6A) modification has been shown to play important role in skeletal muscle development. Wenchang chickens are commonly used as a high-quality animal model in researching meat quality. However, there have been no previous reports regarding the profile of m6A and its function in the embryonic breast muscle development of Wenchang chickens. In this paper, we identified different developmental stages of breast muscle in Wenchang chickens and performed m6A sequencing and miRNA sequencing in the breast muscle of embryos. Embryo breast muscles were weighed and stained with hematoxylin–eosin after hatching. We found that myofibers grew fast on the 10th day after hatching (E10) and seldom proliferated beyond the 19th day after hatching (E19). A total of 6,774 differentially methylated genes (DMGs) were identified between E10 and E19. For RNA-seq data, we found 5,586 differentially expressed genes (DEGs). After overlapping DEGs and DMGs, we recorded 651 shared genes (DEMGs). Subsequently, we performed miRNA-seq analysis and obtained 495 differentially expressed miRNAs (DEMs). Then, we overlapped DEMGs and the target genes of DEMs and obtained 72 overlapped genes (called miRNA-m6A-genes in this study). GO and KEGG results showed DEMGs enriched in many muscle development-related pathways. Furthermore, we chose WNT7B, a key regulator of skeletal muscle development, to perform IGV visualization analysis and found that the m6A levels on the WNT7B gene between E10 and E19 were significantly different. In conclusion, we found that miRNAs, in conjunction with m6A modification, played a key role in the embryonic breast muscle development of Wenchang chickens. The results of this paper offer a theoretical basis for the study of m6A function in muscle development and fat deposition of Wenchang chickens.